Pyrotechnic initiators



J. W. DUNCAN 2 Sheets-Sheet 1 ATTORNEYS Dec. 5, 1967 Filed Nov. 17, 1965 m M W D W 5 E M J W mfifi E g 47 airy. m 9 a Dec. 5, 1967 J. w. DUNCAN 3,356,025

PYROTECHNIC INITIATORS Filed Nov. 17, 1965 2 Sheets-Sheet 2 5 w /2 v5 I f Q :R I a z: 1\ 5Q i g k INVENTOR Q m: Jhmss W DUNCAN q k\\\\\\\\\\\\\\\\\ BY awa f m ATTORNEYS United States Patent 3,356,025 PYROTECHNIC INITIATORS James W. Duncan, Arden, N.C., assignor to Stencel Aero Engineering Corporation, Arden, NC, a corporation of North Carolina Filed Nov. 17, 1965, Ser. No. 508,346 4 Claims. (Cl. 102-39) ABSTRACT @F THE DHSCLOSURE Provides a pyrotechnic initiator having a plurality of primers arranged to be actuated simultaneously by separate actuating elements simultaneously impacted by a striker having an annular tip the arrangement being such that the annular tip of the striker impacts all of the primer actuating elements regardless of the angular disposition of the striker relative to the actuating devices, indexing of the striker therefore being unnecessary.

This invention relates to pyrotechnic initiators of the general type in which operation of an impact-actuated primer serves to ignite a pyrotechnic charge to generate combustion gases for operation of any of various kinds of devices. More particularly, the invention deals with such initiators employing a plurality of primers for redundancy.

Pyrotechnic initiators are widely used in applications requiring certainty of operation, and it therefore has long been recognized that provision of a plurality of simultaneously actuated primers is desirable in order to assure successful operation even in the event of failure of a primer. The primers employed are conventional impact operated devices, and it is known to employ a springdriven striker arrangement, for example, for simultaneously actuating two or more of the primers. Such arrangements have not heretofore been entirely satisfactory, however, because it has been necessary to index or specially orient the striker relative to the primers in order to achieve proper simultaneous actuation of the primers.

A general object of this invention is to provide a pyrotechnic initiator equipped with a plurality of primers and a striker device for simultaneously actuating the primers and wherein operation of the striker device is always efiective to actuate the primers without requiring any special indexing of the striker device relative to the primers.

Another object is to devise a simplified, more dependable pyrotechnic initiator atfording redundancy of primer operation.

In order that the manner in which these and other objects are achieved in accordance with the invention can be understood in detail, one particularly advantageous embodiment of the invention will be described with reference to the accompanying drawings, which form a part of this specification, and wherein:

FIG. 1 is a longitudinal sectional view, with some parts shown in elevation, of an assembled pyrotechnic initiator;

FIG. 2 is a transverse sectional view taken on line 2-2, FIG. 1;

FIG. 3 is an end elevational view of a portion of the initiator of FIG. 1;

FIG. 4 is a longitudinal sectional view taken on line 4-4, FIG. 3;

FIG. 5 is a fragmentary longitudinal sectional view taken on line 5-5, FIG. 4; and

FIG. 6 is a transverse sectional view taken on line 6-6, FIG. 4.

Referring now to the drawings in detail, the illustrated embodiment of the invention is shown as applied to a parachute spreading gun of the type disclosed in copend- Patented Dec. 5, 1967 ing United States patent application Ser. No. 439,568, filed Mar. 15, 1965, by Fred B. Stencel et al., now Patent 3,281,098. The spreading gun typically includes a cylindrical body 1 having an outwardly projecting transverse fiange 2 intermediate the ends of the body. Body 1 defines a cylindrical chamber 3 which is closed at one end of the body and which opens through end portion 4, this portion being provided with internal threads at 5. Flange 2 has outwardly opening radial bores 6 to accommodate the parachute spreading projectiles (not shown), bores 6 communicating with chamber 3 via ports 7.

As best seen in FIG. 4, the device empioys a cartridge assembly including a main powder charge 3 in a cylindrical shear casing 9. A powder case 10 is telescopically attached to the open end of shear casing 9 to complete the enclosure for charge 8 and to support a dual primer assembly. Case 10 has a transverse annular inwardly projeting shoulder 11 which supports a thin, rupturable retaining disc 12, a first cylindrical metal body 13, and a second cylindrical metal body 14. Body 13 is provided with two parallel cylindrical bores 15 and 16, and with a circular centrally disposed recess 17 which is closed by disc 12 and with which bores 15 and 16 communicate. Bores 15 and 16 are spaced apart along a diameter of body 13 and are spaced equally from the center of the body. Body 14 has one fiat face 18 disposed in direct engagement with the face 19 of body 13 which is opposite disc 12. The other flat face 20 of body 14 is exposed, constituting one end of the cartridge assembly. Face 20 is interrupted by a cylindrical recess 21, FIG. 3. Body 14 includes two identical cylindrical primer-accommodating recesses or cavities 22 and 23 which are identical and open through face 18, recesses 22 and 23 being spaced apart along a diameter of body 14 and spaced equally from the center of the body so that, When bodies 13 and 14 are assembled in the manner seen in FIG. 4, the recesses 22 and 23 open toward and communicate with bores 15 and 16, respectively. Body 14 is provided with a cylindrical bore 24 which is coaxial with bore 15, one end of bore 24 opening into recess 22, the other end opening through the bottom wall of recess 21. Similarly, a second cylindrical bore 25 is provided Which is coaxial with bore 16 and opens at one end into recess 23, the other end of bore 25 opening through the bottom wall of recess 21, bores 24 and 25 being identical. At its end opening into recess 21, bore 24 is formed with a transverse annular shoulder 24'. Similarly, bore 25 has a transverse annular shoulder 25'.

Body 14 constitutes a primer housing, while body 13 constitutes a retainer for a black powder initiating change 26 disposed in recess 17. Primers 27 and 28, of identical conventional construction for impact actuation, are contained in recesses 22 and 23, respectively, and are equipped with spherical steel actuating balls 29 and 3% respectively, with ball 29 being disposed in bore 24 and ball 30 in bore 25. Bores 24 and 25 are shorter than the diameter of balls 29 and 3%). With the device assembled and ready for operation, primers 27 and 28 completely fill the respective recesses 22 and 23. Accordin'gly, balls 29 and 30 are engaged between the respective primers and the respective shoulders 24' and 25', and identical portions of the balls project from bores 24 and 25, respectively, into recess 21. Since the balls are identical, and bores 24 and 25 are identical and have identical relationships with respect to recess 21 save for their angular displacement from each other, each ball 29, 3!) projects into recess 21 by precisely the same amount.

In order to assure proper axial alignment of recesses 22 and 23 of body 14 with bores 15 and 16, respectively, of body 13, body 13 is provided with a diametrically a spaced pair of recesses 13', and body 14 has diametrically spaced bores each accommodating a pin 14, the pins 14' projecting beyond face 18 for engagement respectively in recesses 13', as seen in FIG. 5.

As seen in FIG. 1, the cartridge assembly completely fills chamber 3 to a point immediately adjacent threaded portion 5. The remaining portion of chamber 3 is closed by one end portion of the body 31 of a firing assembly, this portion of body 31 being exteriorly threaded and engaged with the threads of portion 5 of body 1. Body 31 is in the form of a cylindrical tube having an outer transverse flange 32 engaged with the end of body 1. The inner wall 33 of body 31 is a plain cylindrical surface, interrupted by a transverse annular inwardly opening groove 34. Wall 33 slidably embraces a cylindrical plunger or striker 35 having a closed end 36 and an axially recessed end portion 37. The end portion of body 31 to which the recessed end 37 is directed includes a transverse centrally apertured wall 38 and a helical compression spring 39 is interposed between wall 38 and end portion 37.

A firing pin 40 extends through the central aperture of wall 38 and projects into an axial recess 41 in striker 35. The tip portion of pin 40 is provided with a transverse annular outer groove 42 of semi-circular transverse cross section. Body 31 is provided with a plurality of bores 43 which extend radially outwardly, communicating between recess 41 and the exterior of body 31, each bore 43 accommodating a spherical ball 44. An actuating line 45 is attached to the end 46 of pin 40 which projects outwardly beyond wall 38.

The end of striker 35 which is directed toward the cartridge assembly terminates in a flat transverse face 47 which, since it extends at right angles to the longitudinal axis of the striker, is parallel to face 20 of body 14 in the completed assembly. Projecting from face 47 axially of the striker is a tubular cylindrical tip 48 of a diameter and wall thickness such as to be accommodated freely by recess 21, without sliding contact with the walls of the recess, as will be clear from FIG. 2. Striker tip 48 has a length significantly greater than the depth of recess 21.

Body 1 has an interior transverse annular shoulder 49 engaged by a shoulder on shear casing 9. The tip of body 31 directly engages face 20 of body 14. Accordingly, with body 31 fully threaded into body 1, so that flange 32 engages the end of body 1, the cartridge assembly occupies a predetermined position in body 1 determined by engagement of the shear casing with shoulder 49. Since the position of the cartridge assembly is predetermined, the axial positions of face 20 and recess 21 are also predetermined, both with respect to body 1 and with respect to body 31.

End portion 46 of pin 40 is enlarged so that, with balls 44 held engaged in groove 42 by reason of their contact with Wall 33, and with the effective combined length of pin 40 and striker 35 then being substantially less than the space between the outer face of wall 38 and the bottom of recess 21, spring 39 causes end portion 46 of the firing pin 40 to shoulder against wall 38, and the free end of tip 48 is spaced a significant distance from the balls 29 and 30, as will be clear from FIG. 1.

When an actuating strain is applied to pin 40 via line 45, the pin is axially withdrawn, with spring 39 being compressed and with balls 44 rolling on wall 33 so that striker 35 is forced to move with pin 40. When pin 40 has been withdrawn far enough to bring balls 44 into alignment with groove 34, the balls are cammed outwardly by the trailing edge portion of groove 34, and the engagement of balls 44 in groove 34 is thus eliminated, the depth of groove 34 being adequate to allow enough outward radial movement of balls 44 to allow the full diameter of pin 40 to be accommodated, striker 35 thus being freed from the firing pin 40. This action allows the spring 39 to project striker 35 toward the cartridge assembly, so that tip 48 strikes balls 29 and 3t) to actuate primers 27 and 28. Since the end of tip 48 is a fiat annular face lying in a plane at right angles to the longitudinal axis of the cartridge assembly, and since both balls 29 and 30 project into recess 21 by the same amount, tip 48 engages both balls 29 and 30 simultaneously so that the two primers are actuated simultaneously (assuming no primer failure).

Since the end face of tip 48 is a complete circular surface, and since tip 48 is freely accommodated by recess 21, this simultaneous actuation of the two primers is completely independent of the rotational position of striker 35 relative to body 1 and the cartridge assembly, and there is accordingly no requirement that the firing mechanism be specially indexed to match the angular disposition of the diameter on which balls 29 and 30 lie.

Though one particularly advantageous embodin'ient of the invention has been chosen for illustrative purposes, various changes and modifications can be made therein without departing from the scope of the invention as defined in the appended claims.

I claim:

1. In a pyrotechnic initiator, the combination of a primer housing provided with at least two primeraccommodating cavities, said primer housing including means defining an annular recess opening outwardly relative to the primer housing, said cavities being spaced axially from said recess and arranged in an annular series axially aligned with said recess, there being a plurality of bores each communicating between said recess and a different one of said cavities;

a plurality of primer actuating elements movably retained each in a different one of said bores,

said primer actuating elements projecting from said bores into said annular recess when said primers are respectively situated in said cavities;

a striker having an annular tip dimensioned for insertion into said annular recess; housing means for said striker, said housing means positioning said striker for rectilinear movement along an axis coincident with the central axis of said recess;

means releasably retaining said striker in a retracted position in which said tip is spaced a substantial distance axially from said primer actuating elements when the latter project from said bores into said recesses; and

means for forcibly driving said striker in a direction to cause said tip to move within said recess and into simultaneous engagement with said primer actuating elements with such engagement being independent of the relative angular dispositions, about the common axis of said tip and said recess, of said tip and said primer actuating elements.

2. A pyrotechnic initiator according to claim 1 and further comprising a cartridge assembly including casing means, and

a pyrotechnic charge carried by said casing means and arranged to be ignited by action of primers carried by said primer housing,

said primer housing constituting a closure for said casing means.

3. A pyrotechnic initiator according to claim 1, wheresaid annular recess has cylindrical side walls, and

said annular tip of said striker is cylindrical and has a wall thickness smaller than the space between said side walls, said tip of said striker being free to move within said recess without sliding friction.

4. In a device of the type described, the combination of a cartridge assembly comprising casing means, a pyrotechnic charge carried by said casing means, a primer housing secured to said casing means and forming a closure therefor, said housing having 6 a striker, a striker housing in which said striker is disposed,

and actuating means for moving said striker in a prea plurality of primer-accommodating cavities, an 5 determined path of travel,

annular recess opening outwardly of said casing said striker having an annular tip capable of free means, and a plurality of bores each opening at movement within said recess toward said primer one end into a different one of said cavities, the actuating elements; and

other ends of all of said bores opening through rigid means supporting both said cartridge assembly the bottom wall of said recess, 10 and said firing mechanism,

a plurality of primer actuating elements each movsaid firing mechanism being so positioned that ably disposed in a different one of said bores, movement of said striker in said predetermined and path of travel causes said annular tip to move a plurality of primers each disposed in a diiferent within said recess and into simultaneous imone of said cavities and positioned in engagepacting engagement with said primer actuating ment with the corresponding one of said actuating elements, said bores each having a shoulder at the end thereelements.

References Cited UNITED STATES PATENTS of which opens through the bottom wall of said recess, said actuating elements being identical 5225 and of such dimensions as to be held 1n en- 2,363,024 11/1944 Thibodeau gagement between said primers and said shoulders, said actuating elements when so engaged all projecting into said recess by a predetermined distance;

firing means comprising SAMUEL FEINBERG, Primary Examiner.

BENJAMIN A. BORCHELT, Examiner.

G. H. GLANZMAN, Assistant Examiner. 

1. IN A PYROTECHNIC INITIATOR, THE COMBINATION OF A PRIMER HOUSING PROVIDED WITH AT LEAST TWO PRIMERACCOMMODATING CAVITIES, SAID PRIMER HOUSING INCLUDING MEANS DEFINING AN ANNULAR RECESS OPENING OUTWARDLY RELATIVE TO THE PRIMER HOUSING, SAID CAVITIES BEING SPACED AXIALLY FROM SAID RECESS AND ARRANGED IN AN ANNULAR SERIES AXIALLY ALIGNED WITH SAID RECESS, THERE BEING A PLURLITY OF BORES EACH COMMUNICATING BETWEEN SAID RECESS AND A DIFFERENT ONE OF SAID CAVITIES; A PLURALITY OF PRIMER ACTUATING ELEMENTS MOVABLY RETAINED EACH IN A DIFFERENT ONE OF SAID BORES, SAID PRIMER ACTUATING ELEMENTS PROJECTING FROM SAID BORES INTO SAID ANNULAR RECESS WHEN SAID PRIMERS ARE RESPECTIVELY SITUATED IN SAID CAVITIES; A STRIKER HAVING AN ANNULAR TIP DIMENSIONED FOR INSERTION INTO SAID ANNULAR RECESS; HOUSING MEANS FOR SAID STRIKER, SAID HOUSING MEANS POSITIONING SAID STRIKER FOR RECTILINEAR MOVEMENT ALONG AN AXIS COINCIDENT WITH THE CENTRAL AXIS OF SAID RECESS; MEANS RELEASBLY RETAINING SAID STRIKER IN A RETRACTED POSITION IN WHICH SAID TIP IS SPACED A SUBSTANTIAL DISTANCE AXIALLY FROM SAID PRIMER ACTUATING ELEMENTS WHEN THE LATTER PROJECT FROM SAID BORES INTO SAID RECESSES; AND MEANS FOR FORCIBLY DRIVING STRIKERS IN A DIRECTION TO CAUSE SAID TIP TO MOVE WITHIN SAID RECESS AND INTO SIMULTANEOUS ENGAGEMENT WITH SAID PRIMER ACTUATING ELEMENTS WITH SUCH ENGAGEMENT BEING INDEPENDENT OF THE RELATIVE ANGULAR DISPOSITIONS, ABOUT THE COMMON AXIS OF SAID TIP AND SAID RECESS, OF SAID TIP AND SAID PRIMER ACTUATING ELEMENTS. 